This invention relates to tripot style joints and, more particularly, to a tripot joint having a retainer for needle rollers.
A tripot style joint is usable as one type of constant velocity (“CV”) joint on a drive axle of a vehicle. A CV joint is used to transfer a uniform torque and a constant speed, while operating through a wide range of angles. The CV joint is preferably quite compact so as to allow the drive axle to rotate at a constant velocity, regardless of the operating angle.
Turning now to FIGS. 1 and 2, a tripot style joint 10 includes a tripot housing 12 formed with a ball guide, the interior grooves of the housing 12. That is, the housing 12 has an offset radius profile for the ball bore and an outer ball guide to help track the outer ball relative to die housing axis. A tripot spider 14 includes a somewhat spherical trunnion 16, a ball assembly 18 having an inner ball 20, a complement of needle rollers 22, and an outer ball 24. The inner ball 20 has a spherical radius profile on the inner diameter that mates to the spherical profile of die spider trunnion 16 and a cylindrical outer diameter that mates with the needle rollers 22. The complement of needle rollers 22 mates to the outer diameter of the inner ball 20 and the inner diameter of the outer ball 24. The outer ball 24 has a cylindrical inner diameter and a radius profile outer diameter to match the ball bore of the housing 12. As shown in FIG. 2, the inner diameter of the outer ball 24 is designed with two shoulders 26 that form a cup. The cup area contains the complement of needle rollers 22.
The primary function of such a tripot joint 10 is to reduce axial forces generated during the operation of the joint 10 within a vehicle. The generated axial forces create a ride disturbance in the vehicle called “shudder”. The reduction to the generated axial forces is accomplished by tracking either the outer ball 24 or the ball assembly 18 relative to the axis of the housing 12.
The ball assembly 18 also requires some means of retaining the needle rollers 22 within the interior of the outer ball 24. The design shown in FIGS. 1 and 2 utilizes an integral flange 26 to retain the needle rollers 22 within the outer ball 24. However, the inner diameter profile of the outer ball 24 that forms flange 26 is expensive to manufacture. In most cases, the flange 26 is through-hardened due to its cross-sectional shape and the types of materials used in fabricating the outer ball. To achieve sufficient strength in the through-hardened flange 26 for retaining the needle rollers 22 within the interior of the outer ball 24, it is often necessary to increase the cross-sectional thickness of the flange, resulting in an increase in the overall package size of the joint. In addition, flange 26 may have sufficient strength to retain the needle rollers during assembly of the joint, yet fail to retain the needle rollers during actual operation of the joint.